Up to 1,000 workers at Newry, Mourne and Down DC are to strike following a row about pay and conditions.
Four trade unions said staff would strike in the run-up to Christmas after claims the council's chief executive had failed to deal with the workers' concerns or meet directly with unions.
A union statement read: ‘It is with regret that we are being forced to take this action in order to improve our pay and protect our terms and conditions.
'Although there will be limited action in December, our members will be escalating the dispute if the issues are not resolved, in January 2021.
'It is in the management's hands to resolve this dispute.'
The council insisted it had been working with the unions and its chief executive had attended a series of meetings with them.